1. Field of the Invention
This invention relates to devices for mixing particulate solids, and more particularly, to a pin mixer having a rotor with a plurality of radially extending pins for mixing the particulate solid material and for transporting the material through the apparatus.
2. Description of the Prior Art
Pin mixers for mixing particulate solids generally have helically disposed pins attached to a rotor. An example of such an apparatus is disclosed in U.S. Pat. No. 3,787,161 to Frye et al., in which the pins form a double helix on the rotor with the pins of one helix axially staggered with respect to the other. While the apparatus of the present invention utilizes pins arranged to form a plurality of helices which are axially staggered, the pins in the present invention are also angularly staggered which has proven to increase contact of the material by the moving pins for better mixing and transport through the apparatus. Another patent showing two axially staggered helices is U.S. Pat. No. 3,011,876 to Raistrick.
The pin mixer of Driscoll, shown in U.S. Pat. No. 3,636,188 utilizes an inwardly extending dam adjacent the outlet. The pin mixer of the present invention has an externally adjustable baffle adjacent the outlet and another adjustable baffle opposite the first baffle. Thus, the area between the baffles and the rotor can be varied depending upon the mixing time desired within the apparatus. This is distinguishable from Driscoll which has a stationary dam. U.S. Pat. No. 2,920,344 to Stirling shows a plurality of radially extending baffles projecting inwardly in a mixing apparatus. The baffles are spaced longitudinally along the apparatus, and are not externally adjustable as are the baffles of the present invention.
U.S. Pat. No. 3,163,403 to Engels discloses a mixing machine having a disc attached to, and rotatable with, a shaft, which disc is used to retain a substantial portion of the material to be mixed near the circumference of the outer shell of the apparatus. The discs attached to the rotor of the pin mixer of the present invention are distinguishable in their function in that they are utilized in conjunction with a pressure source to assure that leakage through the apparatus is away from shaft seals. Further, the pressure acts to keep material from collecting around the outer peripheral edge of the discs.